Refrigeration method and apparatus



Dec. 24, 1963 w. H. HOGAN 3,115,016

REFRIGERATION METHOD AND APPARATUS Filed July` 30, 1962 16 Sheets-Sheet 1 Dec. 24, 1963 w. I-I. HOGAN 3,115,016

REFRIGERATION METHOD AND APPARATUS Filed July 30, 1962 16 sheets-sheet 2 3o 32 3e 5e 3o 32 3e 5e I 26/ /lo 26/ fo *'25 I/28 I Ia/ 2e 22\I 22 w /24 47 I? I4 47 I7 I4 I J Jv 47 '-I I 47 I-I I5 l5 I8 I l F|g 5 vF Ig 6 REGENERAToI-'I r- I oss u I NET l g REFRIGERATION I D: LLI D. I- \TR03+4 QROS+4 \J Tco3+4 TcoI+2 I I I f I FIRST STEP SECOND STEP THIRD STEP FOURTH STEP INVENTOR. F Ig. 7

Wolter H. Hogan At o ney Dec. 24, 1963 W. H. HOGAN REFRIGERATION METHOD AND APPARATUS Filed July 30, 1962 DOWN OPEN

CLOSED OPEN CLOSED 16 Sheets-Sheet 3 STEP I STEP 2 STEP 5 STEP 4 DISPLACERS INI ET VALVES I I f .FIRST f TI-IIRD I AND SECOND ,f AND FDURTHI SPAcI-:s sPAcI-:s I I l l I, EXHAUST vALvEs /TTHIRD FIRST :AND FouRTI-I ,g AND sEcoND f SPACES I lsPAcEs I 1 l I l F Ig. 8

Walter H. Hogan Dec. 24, 1.963 bw, H, HOGAN 3,115,016

REFRIGERTION METHOD AND APPARATUS Filed July 50, 1962 16 Sheets-Sheet WuITer H. Hogan Afror y Dec. 24, 1963 w, H, HOGAN 3,115,016

REFRIGERATION METHOD AND APPARATUS Filed July 30, 1962 16 Sheets-Sheet 5 36 3e 3e 3a es es 39 3| 33 l Q-T- 3| 3 /72 74 73 7 2 74 73 2e e5 /28 26/ e5 /28 /22 si /22 es l 23 67 /le 244., /25 23 ,le i? /25 V41 6g a 47 Y 47 22 7 22 VL] j l L I I l Fig. l5 Fig. le

lNvENToR Wolter H. Hogan BY /kmz Z A110 n y Dec. 24, 1963 W. H. HOGAN REFRIGERATION METHOD AND APPARATUS Filed July 30, 1962 16 Sheets-Sheet 6 2f? 23 |6/ 47 e4\ nl 57 L 2.21 47 L Fig. |7 Fig. le

3| 33 )@1- A36E 74 73 66E 74 73 2e /28 26/ ,28

22 68 22 QQ L 2/4 65 24 65 23 ,le 47 ,25 23 /le 47 25 22 47 7 0 22 47 1Q I I 4 e7 67 Fig. I9 F'g- 20 INVENTOR Wolter H. Hogan BY Dec. 24, 1963 W. H. HOGAN REFRIGERATION METHOD AND APPARATUS Filed Juiy 50, 1962 16 sheets-sheet 7 STEP I STEP 2 STEP s STEP 4 uP f PISTONSI DowN vALvE CONTROLLING FIFTH SPACE OPEN I o@ I o v v A I CLOSED I l INI ET OPEN ,I THIRD II AND SECOND lf' AND FOURTH, SPACES l' SPACES I CIEOsI-:D

i EXHAUST VALVES I OPEN -L ,I THIRD .Il FIRST IAND FOURTH AND SECOND ,f iSPACES i SPACES CLOSED I I I I 90 IeO 27o 36o F Ig. 2|

INVENTOR. Walter H. Hogan BY I /ZME Dec. 24, 1963 W. H. HOGAN REFRIGERATION METHOD AND APPARATUS Filed July 30, 1962 16 Sheets-Sheet 8 Fig. 24

IN VENTOR Wolter H Hogan Dec. v24, 1963 w. HOGAN 3,115,016

REFRIGERATION METHOD AND APPARATUS Filed July 50, 1962 16 Sheets-Sheet 9 Attorney Dec. 24, 1963 w. H. HOGAN 3,115pl6 REFRIGERATION METHOD AND APPARATUS Filed July 50, 1962 16 Sheets-Sheet l0 IBI F INVENTOR Wolter H. Hogan Dec. 24, 1963 w. H. HOGAN 3,115,016

REFRIGERATION METHOD AND APPARATUS Filed July so, 1962 1e sheets-sheet 11 INVENTOR Walter H. Hogan Dec. 24, 1963 w. H. HOGAN 3,115,016

REFRIGERATION METHOD AND APPARATUS Filed July 50, 1962 16 Sheets-Sheet 12 /ae /lo 24 es es 26o x( 4o L /265 4I \45 E l l l \2s4 faoo 260 1 :265

2 206 4 7- (Vzo 2|3\ Flg. 28

1NvENToR Walter H. Hogan l BY A At rney Dec. 24, 1963 w. H. HOGAN 3,115,016

REFRIGERATION METHOD .AND APPARATUS Wolter H. Hogan Dec. .24, 1963 w. H. HOGAN REFRIGERATION METHOD AND APPARATUS 16 Sheets-Sheet 14 Filed July 50, 1962 Rn mw. u No n l 3 WH/,r H ...n 3 3 WWA G.. H. g ...d M (W V.. B e w @zlgm 2 @11 m. d 2 F 3 .wl Q. F

Til-T n4 Dec. 24, 1963 Filed July 30, 1962 W. H. HOGAN REFRIGERATION METHOD AND APPARATUS 16 She ets-Sheet 15 OPEN l l l l l I vALvE 27e CLOSED loPEN 279 CLOSED j oPEN 283 CLOSED I oPEN 287 cLosED l I oPEN 285cLosED l L oPEN 289 cLosEo l oPEN n HP 5i l \.\`L\n\ suPPLY CLOSED vALvEs 37 OPEN j cLosEn OPEN l um LP Lun- EXHAUST ggg vALvEs 39 cLosED -l F lg. 36 L INVENTOR Walter H. Hogan Dec. .24, 1963 Filed July 30, 1962 Q GROSS REFRIGERATION 8 REFRIGERATION LOSSES 16 Sheets-Sheet 16 GROSS REFRIGERATION NET REFRIGERATION, CASE I REGENERATOR PERFORMANCE CASE I A REGENERATOR LOSSES, CASE I REGENERATOR PERFORMANCE NET CASE2 CASE 2 FIXED LOSSES,

REGENERATOR CASE I I I l l REFRIGERATION, I l I I I FlxED Losses, cAsE 2 f(N,v, AP)- Fig. 37

INVENTOR Wolter H. Hogan im' /yw/ A'r orney United States Patent O 3,115,016 REFRIGERATION METHOD AND APPARATUS Walter H. Hogan, Wayland, Mass., assgnor to Arthur D. Little, Inc., Cambridge, Mass., a corporation of Massachusetts Filed `luly 30, 1962, Ser. No. 213,185 49 Claims. (Cl. 62-6) This invention relates to refrigeration method and apparatus and more particularly to a method and apparatus for attaining low temperatures economically.

There are described and known in the prior art a number of cycles and their apparatus for achieving refrigeration. Many such cycles are based upon the use of expansion engines or turbines. Others involve complicated heat exchange systems, while still others (although somewhat more simple in design) require tightly-fitting pistons and sealing rings which must be capable of operation under extremely low temperatures.

In order to overcome the disadvantages inherent in the prior art refrigeration cycles, method and apparatus were developed for materially lessening these disadvantages. These methods and apparatus are the subject of U.S. Patents 2,906,101, 2,966,034 and 2,966,035. In these patents there are described and claimed novel refrigeration methods and apparatus, the method and apparatus of U.S. Patent 2,966,035 being directed to a so-called no work cycle in which refrigeration is obtained by removing more sensible heat from the system than is taken into the system by the refrigerating fluid used. Although the cycle described in U.S. Patent 2,966,035 has been found to be very successful in producing refrigeration even as low as 4.2" K., the method and apparatus of this cycle possess an inherent disadvantage in that the hot and cold ends of the apparatus are thermally connected since they are both within a single cylindrical housing. This thermal connection is responsible for loss in efficiency due to transfer of heat from the hot to the cold end. This is true even though such modifications as loose-fitting displacers, heat stations and the like are employed in connection with the basic method and apparatus. The limitation in efficiency which can be attained with the method and apparatus described in U.S. Patent 2,966,035 is due to the unavoidable heat transfer which takes place within the system. It will be appreciated that for attaining extremely low temperatures of the order of 4.2 K. (the liquefaction point of helium) this heat transfer is of particular importance. In the method and apparatus of U.S. Patent 2,9366,035 this heat transfer is greatly reduced but is still present to some extent. The problem therefore becomes one of not only reducing but of eliminating the heat leak from the hot to the cold zones. I have found that by the use of a double acting System it is possible to eliminate this heat leak and thereby to provide method and apparatus for refrigeration which is not only extremely efficient at higher temperatures but also at the Very low temperatures.

It is therefore the primary object of this invention to provide a novel refrigeration method which eliminates the transfer of heat between the hot and cold zones, a factor which is a major cause of loss of efllciency in most refrigeration methods. It is another object of this invention to provide a method of the character described which is capable of producing refrigeration down to or even below 42 K., i.e., is capable of liquefying He4 and even He3. It is another object of this invention to provide such a method which is flexible in operation and versatile in its application in connection with other methods, for example maser operation or infra-red detection.

It is another primary object of this invention to provide an apparatus for refrigeration which eliminates heat transfer between the hot and cold portions of the apparatus.

ice

It is another object to provide apparatus of the character described which is efficient, flexible in arrangement, and permits use with other apparatus. It is another object to provide refrigeration apparatus which permits the incorporation of auxiliary heat exchange means to attain extremely low temperatures. Yet another object is to provide a low temperature apparatus which can be made in extremely small sizes for use as a source of refrigeration in many devices such as space vehicles, missiles, etc. Other objects of the invention will in part be obvious and in part be apparent hereinafter.

The method of this invention may be described in terms of a cycle which comprises the steps of:

(a) delivering high-pressure fluid from a high-pressure fluid source into communicating first and second spaces and compressing residual low-pressure fluid in the first space thereby to heat the residual fluid, while simultaneously dischaging high-pressurev fluid from communieating third and fourth enclosed spaces into a low-pressure region, thereby cooling the fluid in the fourth space;

(b) continuing delivery of the high-pressure fluid from the high-pressure fluid source and transferring heated fluid from the first space to the second space, while simultaneously continuing discharging fluid from the fourth space thereby reducing its pressure to that of the low-pressure region and to the third space where it becomes residual fluid;

(c) throughout delivery and discharge of steps (a) 'and (b) extracting heat from the high-pressure fluid thereby to cool it initially and transferring heat to the low-pressure fluid thereby to heat it initially;

(d) expanding the highpressure fluid in the second space to cool it further by discharging it into a low-pressure region, while simultaneously supplying high-pressure fluid from a high-pressure fluid source to the third and fourth spaces and compressing residual low-pressure fluid in the third space delivered thereto in step (b) thereby to heat the residual fluid;

(e) continuing transfer of low-pressure fluid from the second space to the low-pressure region and to said first space to become the low-pressure residual fluid of step (a), while simultaneously continuing delivery of the highpressure fluid from the high-pressure fluid source and transferring heated fluid from the third space to the fourth space; and

(f) throughout discharge and delivery of steps (d) and (e) transferring heat to the low-pressure fluid to heat it initially while extracting heat from the high-pressure fluid to cool it initially, thereby establishing the conditions to begin step (a).

As will be apparent in the detailed description which follows, this cycle is also of the no work type, i.e., the energy extracted (and hence the refrigeration produced) is in the form of thermal energy. In my copending application Serial No. 213,184 filed at the same time as this application I have disclosed the corresponding work cycle in which the energy delivered external of the system is mechanical energy.

The basic apparatus of this invention comprises a first warm chamber of constant volume, a second cold chamber of constant volume, mechanically connected first and second displacer means movable within the first and second chambers, respectively, and adapted to define within each chamber upper and lower subchambers of variable volumes; first passage means communicating between the upper subchamber of the first chamber and the lower subchamber of the second chamber; second passage means communicating between the lower subchamber of the first chamber and upper subchamber of the second chamber; supply reservoir means for supplying high-pressure fluid, exhaust reservoir means for receiving low-pressure fluid; and heat exchange means associated with the first and second passages and adapted to transfer heat between the high-pressure and low-pressure fluids as they are transferred within the system.

As will be apparent in the following description, modifications are possible in the passage means and in the heat transfer means. There may also be a third auxiliary chamber having a piston mechanically connected to the displacers and used to balance the pressures within the chambers, provided the hot and cold chambers are not of the same volume. It is also possible to combine with the basic apparatus auxiliary heat exchange means to increase the eliiciency of the apparatus and to permit the attaining of extremely low temperatures. All of these modifications will be described in detail below.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination of elements and arrangements of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure. The scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIGS. 1-6 are simplified diagrammatic views of the apparatus of this invention illustrating the steps in the basic cycle;

FIG. 7 is a diagrammatic representation of the temperature conditions existing in the first and third enclosed spaces and simultaneously in the second and fourth enclosed spaces;

FIG. 8 illustrates a typical operational sequence for the cycle of the apparatus of FIGS. l6;

FIG. 9 illustrates a modification of the apparatus showing the use of a countercurrent heat exchanger;

FIG. 10 illustrates another modification of the apparatus showing the use of a combination of a countercurrent heat exchanger with a regenerator;

FIG. 11 is a horizontal cross-section of a typical combination heat exchanger and regenerator such as shown in FIG. 10;

FIG. 12 is a fragmentary vertical cross-section of the heat exchanger of FIG. 11;

FIGS. 13-20 are simplified diagrammatic views of a modification of the apparatuss of FIGS. 1-6 in which an auxiliary pressure chamber is incorporated;

FIG. 21 illustrates a typical operational sequence for the cycle of the apparatus of FIGS. 13-20;

FIGS. 22 and 23 illustrate modifications of the basic apparatus as represented by FIGS. 1-6 and 13-20, respectively, illustrating how one of the heat exchange means in the form of a regenerator may serve as a physical connection between two of the subchambers;

FIG. 24 illustrates one form of a multiple-displacer, double-acting apparatus;

FIG. 25 is a modification of the apparatus of FIG. 24 in which portions of the heat exchange means in the form of regenerators serve as physical connections between some of the subchambers;

FIGS. 26 and 27 illustrate the use of auxiliary heat exchange systems in connection with the multiple-displacer, double-acting apparatus of FIGS. 24 and 25, respectively, the former showing the use of two different heat transfer fluids and the latter showing the use of a single heat transfer and refrigeration fluid;

FIG. 28 illustrates the use of auxiliary heat exchange systems in connection with the basic apparatus of FIG. 1;

FIG. 29 illustrates in diagrammatic form the use of radiation shielding as part of an insulation system;

FIGS. 30-35 are simplified diagrammatic views of a modification of the apparatus of FIGS. 1-6 illustrating the steps of a modification in the basic cycle;

FIG. 36 illustrates a typical Operational sequence for the cycle of the apparatus Of FIGS. 30-35; and

FIG. 37 is a plot of refrigerator performance showing the inuence of fixed losses on refrigeration efficiency.

Turning now to FIG. l, the basic apparatus may first be described with reference to that drawing before a detailed description of the cycle is given. In FIG. 1 it will be seen that there are provided a hot chamber 10 and a cold chamber 14. It will be appreciated that the terms hot and cold are used in a relative sense, the hot chamber normally being one which is at room temperature or slightly above, whereas the cold chamber is at a temperature approximating that at which refrigeration is available to an external load.

The hot chamber 10 has movable within it a displacer 11 which divides this chamber into an upper subchamber 12 and a lower subchamber 13, the volume of these subchambers being variable and defined by the position of the displacer 11 in chamber 10. In like manner, the cold chamber 14 has movable within it displacer 15 which is mechanically connected to displacer 11 by suitable means such as an essentially gas-tightly sealed connecting rod 16, thus coordinating the movements of displacers 11 and 15. Appropriate displacer movement is achieved through a driving means illustrated as drive wheel 19. Thus, in a similar manner displacer 1S defines within chamber 14 an upper subchamber 17 and a lower subchamber 18, the volumes of these subchambers being variable and defined by the position of displacer 15. Both displacers 11 and 15 are close-fitting within their respective chambers so that they form an essentially gas-tight seal with the walls of the chambers. Because the subchambers of each chamber are at substantially the same temperature the seals do not have to be absolutely gas-tight.

In the following detailed description of this invention reference will be made from time to time to displacers and pistons, and in keeping with common practice the term piston will be used to include a sliding body moving within a cylindrical vessel whether or not it experiences pressure differentials on its surfaces and whether or not it responds to changes in the thermodynamic characteristics of the fluids acting upon its surfaces to generate mechanical work. The term displacer will be reserved for a similar sliding body which experiences essentially no pressure differentials on its surfaces and which generates or delivers no external work. Thus the term piston includes displacers and is used in a generic sense. Where it is possible to construe the role of the sliding body as either, it will be referred to as a piston.

Further with respect to terminolog it will be noted in the detailed description of the apparatus of this invention that the subchambers within the chambers are referred to as upper and lower subchambers. This is done wholly for convenience and to relate the description to the diagrammatic representations in the drawings. It will be appreciated that the apparatus can function in any position or orientation and it is within the scope of this invention to have it do so.

Between chambers 10 and 14 there are two connecting paths: conduit 22 which joins the upper subchamber 12 of the hot chamber 10 with the lower subchamber 18 of the cold chamber 14, and conduit 24 which joins the lower subchamber 13 of the hot chamber 10 with the upper subchamber 17 of the cold chamber 14. In describing these subchambers in terms of a refrigeration method, subchambers 12 and 18 are referred to as the first and second enclosed spaces while subchambers 13 and 17 are referred to as the third and fourth enclosed spaces, respectively.

Located in and associated with the connecting paths, e.g., conduits 22 and 24 are heat exchange means which in the apparatus of FIGS. l-6 are shown as regenerators 23 and 25. Leading into conduit 22 is a branch conduit 26 and leading into conduit 24 is a branch conduit 28. High-pressure fluid is introduced into subchambers 12 and 18 through branch conduit 26 and controlled by valve 31, while the fluid from these subchambers is discharged into low-pressure reservoir 32 through branch conduit 26, the flow being controlled by valve 33. In like manner high-pressure fluid is introduced into subchambers 13 and 17 through branch conduit 28, and its flow is controlled by valve 37; while uid from these subchambers is discharged into the low-pressure reservoir 38 through branch conduit 28, and its iiow is controlled by valve 39.

The temperature of the fluids flowing back and forth in Athose portions of conduits 22 and 28 which join the lower' ends of the regenerators 23 and 25' with subchambers 18 and 17, respectively, will liuctuate relatively widely. For this reason some stabilization in iiuid temperature in these regions is dictated by the necessity for high regenerator eiiiciencies and/ or for a reasonably constant level of refrigeration output. Two alternative arrangements for attaining such stabilization are illustrated in FIGS. l and 2.

The means for fluid temperature stabilization shown in FIG. 1 includes means for delivering refrigeration to an outside or external load. In this apparatus a heat exchanger 45 is provided which is formed in three sections, section 4t) being adapted to effect heat exchange between the fluids flowing in conduit 22 (or 28) with a heat sink 41, formed for example of a mass of lead, or other material which has a high heat capacity in the temperature range represented by the temperature of the cold uid. The third section 42 of the heat exchanger is adapted to effect heat exchange between the heat sink 41 and an external load, such as a suitable heat transfer liuid circulated in conduit 44. It is, of course, also possible to bring an external load (e.g., an infrared detector) in direct thermal contact with the heat sink 41, thus eliminating the heat transfer lluid and conduit 44. By the use of a heat sink of suflicient magnitude it is possible for it to experience fluctuating temperature on the side adjacent section 49 and a substantially constant temperature on the side adjacent section 42.

FIG. 2 illustrates an alternative arrangement which provides heat stations 20 and 21 (such as those illustrated in FIGS. `13 and 14 of U.S. Patent 2,966,035) to stabilize the operation of regenerators 23l and 25, and a separate means for supplying refrigeration from the system through suitable external loads shown as heat exchangers l43 located at the outlet of subchambers 17 and 18. Refrigeration is transferred externally by means of a suitable heat transfer iiuid circulated through heat exchanger 43 by means of a conduit 44. In this case, fluctuations in the refrigeration delivered will be greater than in the apparatus of FIG. l. In the remaining FIGS. 3-6 these alternatives (i.e., heat exchanger 45 or heat exchanger 43 with heat station 20) are merely designated diagrammatically by a box 47 to simplify the drawings.

The refrigeration method of this invention may be now described in terms of a cycle and with reference to FIGS. 1-6. In the figures, valves which are open are indicated by an open circle whereas those which are `closed are indicated -by an x within the circle. It will be appreciated that compressors 34 and coolers 35 which are shown in FIG. l are also present in the apparatus in all of the FIGS. 1-6. Since they are the same they are not repeated in the drawings. In describing the cycle of this invention reference should also be had to FIG. 7 which is a diagrammatic representation of the temperature conditions existing in the subchambers. lIn FIG. 7 the ycurves are identiiied in terms of the ordinal numbers used in claiming the basic cycle by tne use of subscripts identifying the temperature points. The solid line plots the temperature conditions in the `first and second subchambers or enclosed spaces (i.e., subchambers `12 and 18, respectively); while the dotted iine plots the temperature conditions in the third and fourth subchambers `or enclosed spaces (i.e., subchambers 13 and 17, respectively). It is to be understood that FIG. 7 is diagrammatic and no attempt has 4been made to indicate actual temperature levels on a linear or other scale.

Inasmuch as a description of a method such as this must 6 be somewhat stylized when shown diagrammatic drawings (FIGS. 1 6) reference should also be had to FIG. 8 which plots the movement of the displacers and the corresponding sequential operations of the four principal valves (31, 33, 37 and 319) which control lthe iiow of highpressure and low-pressure -iiuids on both sides of the cycle.

Since the cycle must begin at Some point it will be described as beginning with the conditions prevailing in FIG. l just as the high pressure valve 31 and low-pressure valve 319 `are opened. (Valves 33 and 37 are closed.) Now at this instant warm subchamber `12 contains residual lowpressure fluid While cold subchamber 17 contains cold high-pressure fluid. In the following description the subscripts used in connection with temperature T designate the point at which the temperature is determined, that is, SE refers to the temperature of the fluid at the subschamber entry, SO to the fluid temperature at the subchamber outlet, C to the temperature at the compressor outlet, RE to the temperature at the regenerator entry, RO to the temperature at the regenerator outlet, and CO to the iluid temperature at the cold subchamber outlet. 'Ihe numeral subscripts appended to these letter subscripts denote the various chambers involved. Thus, for example, TRE1Jr2 indicates the temperature of the fluid entering the first and second regenenators while TCC,3`+4 indicate the temperature of the fluid leaving Athe cold subchambers 3 and 4. When valve 31 is opened high-pressure iluid at a temperature TSElJrZ (FIG. 7) is delivered from the high-pressure iluid source 30 to the two communicating subchambers 12 and 18, the communication being, of course, through the regenerator 23. With the delivery of high-pressure fluid into subchamber 12 the residual low-pressure tluid contained therein initially at TSO1+2 is compressed and heated. Now it will be seen that the fluid in subchamber 12 is at a ternperature above that which the high-pressure liuid entered the system through conduit 26, namely at T01 +2.

Simultaneously with the delivery of high-pressure iiuid into subchambers 12 and 18, fluid is being discharged t0 the low-pressure reservoir 38. This means that the highpressure cold iluid present in subchamber 17, which had been initially cooled by passage -through regenerator 25 (as will be explained below) is further cooled by expansion. Thus as shown in FIG. 7, the temperature of the high-pressure iiuid in subchamber 17 drops from TROS, to TCO3+4.

With the movements of the fluids within the system in step one it will be appreciated that forces acting on the displacers 11 and 1S maintain them in essentially the positions indicated in FIG. l. During this step the volume of subchamber 112 is essentially equal to that of chamber 1t) and that of subschamber 13 is essentially zero; while the volume of subchamber 1'7 is essentially that of chamber 14 and the volume of subchamber 18 is essentially zero.

During the second step displacers 11 Iand 15 are forced to their uppermost position and are maintained in this position as illustrated in FIGS. 2 and 3. In lthe second step delivery o-f the high-pressure fluid to subchambers 12 and 18 is continued. With the movement of displacers upwardly by virtue of the high-pressure uid entering subchamber 18 and iiuid exhausting from subchamber 17 it is necessary to continue this delivery of high-pressure fluid to maintain the high-pressure side of the system at essentially constant pressure since the volume of the fluid entering subchamber 18 is decreased by vir-tue of the fact that it is initially cooled in its passage through regenerator 23. Ilhus the cold iiuid in subchamber 18 at the end of this step (FIG. 3) remains at high pressure.

With the continued addition of high-pressure iiuid at temperature TSE1+2 the temperature of the high-pressure flu-id delivered to the regenerator 23 will be intermediate between the temperatures of the entering and compressed luids by virtue of lthe mixing of liuids lat TC1+2 and TSE1+2- This temperature is identified as TRE1+2 in FIG. 7. Further, during this second step the high-pressure fluid entering subchamber 18 is initially cooled to the point designated TROU., from TRE1 +2, this initial cooling being accomplished by passage through regenerator 23.

On the now low-pressure side of the system the expanded cold, low-pressure fluid in subchamber -17 returns through regenerator 25 giving up heat and cooling the regenerator. Thus this low-pressure fluid is warmed from TC03+4 to TSOSJF4 as shown in FIG. 7.

In this step a portion of the now warm low-pressure fluid enters subchamber 13 (FIG. 2) to fill this expanding subchamber with warm low-pressure fluid. It will be seen that the temperature T503@ which represents the temperature at which the low-pressure fluid leaves the regenerator and the system is a little less than the temperature at which the high-pressure fluid entered this regenerator at point TRE3+4 as will be explained later.

At the end of this second step (FIG. 3) the volumes of subchamber 18 and of subchamber 13 are essentially equivalent to the volumes of chambers 14 and 10, respectively, while the volumes of subchambers 12 and 17 are essentially zero.

In the third step, illustrated in FIGS. 4 and 5, highpressure valve 31 is closed and low-pressure valve 33 is opened. Simultaneously high-pressure valve 37 is opened and low-pressure valve 39 is closed, thus in essence bringing about the reversal of the cycle. The high-pressure fluid in subchamber 18, as it discharges into the lowpressure reservoir 32, expands and further cools as designated in FIG. 7. There it will be seen that the temperature of this fluid drops `from T-p-mhL2 to TCO1 +2, the lowest point in the refrigeration cycle. Thus the fluid in subchamber `18 has duplicated the performance of the fluid in subchamber 17 in the first step. With highpressure valve 37 open high-pressure fluid is introduced into subchamber 13 wherein the residual fluid contained therein initially at TSO3H is compressed and heated to raise the fluid temperature to TCM.

Thus in similar fashion the high-pressure fluid in subchamber 13 passes through the same temperature cycle as the fluid in subchamber 12 in the first step. As is evident from the build-up of pressure in subchamber 17 and decrease of pressure in subchamber 18 the displacers move downwardly during this step and remain in their lowermost position in the fourth step.

During the fourth step, lthe expanding fluid leaving subchamber 18 returns through regenerator 23 to cool it and itself be warmed to the temperature TsolL2 which is a little less than the temperature at which it entered regenerator 23, namely TRE1 +2, the difference being due to regenerator losses. A portion of this low-pressure fluid fills subchamber 12 to become the residual fluid therein for repetition of the first step described above.

It will be appreciated that inasmuch `as the fluid entered the system at a temperature designated as TSE1+2 (a ternperator lower than that at which it left the system) there is thermal energy taken out of the system in the form of sensible heat. The net refrigeration achieved then is essentially equivalent to the difference between T5011,2 and TSE1 +2. In this same manner refrigeration was achieved in step 2 when the low-pressure fluid was exhausted at a temperature designated TSOSM.

Simultaneously with the delivery of refrigeration from the first -and second subchambers 12 and 18, the delivery of high-pressure fluid is continued to subchamber 17 initially cooling the fluid to the point designated TRO3+1. As in the case of high-pressure fluid entering subchamber 18 is in the second step, this continuing of high-pressure fluid supply means that essentially constant pressure is maintained within the system during step 4 (FIG. 6) thus forcing the displacers to rema-in at their lowermost position and build up a supply of high-pressure cold fluid in subchamber 17 to reach the point in the cycle where the first step begins again.

With the continuation of high-pressure fluid supply the heated fluid of subchamber 13 mixes with the incoming high-pressure fluid to give the high-pressure fluid entering regenerator 25 an intermediate temperature designated at TRE3+4- With the above-described conditions obtaining at the close of step 4 the cycle is lbegun again with step l by closing valves 33 and 37 and opening valves 31 and 39.

Each side of the system is preferably a closed system which requires recompressing the fluid in the low-pressure reservoirs 32 and 38 in a suitable compressor 34 and then cooling in a cooler 35 before storing in the high-pressure supply means 30 and 36. In FIG. 7 the high-pressure fluid is shown being delivered at temperature TSE which is essentially that temperature of the fluid as it is delivered from the high-pressure supply means.

The refrigeration fluids used on each side of the cycle may be the same fluid and may be drawn from a common high-pressure fluid source and exhausted into a common low-pressure reservoir. The fluids on both sides of the cycle may also, of course, be different, in which case separate high-pressure fluid supply means and low-pressure fluid exhaust means must be used for each side as shown in FIG. 1.

Temperature stabilization during fluid flow is attained through the use of heat exchanger 45 (FIG. l) or the combination of heat stations 20 and 21 and heat exchangers 43 (FIG. 2). The manner in which refrigeration is supplied to an external load has been described above in connection with the discussion of FIGS. 1 and 2.

In FIGS. l-6 the heat exchange between the high-pressure and low-pressure fluids was achieved through the use of regenerators 23 and 25. Other methods and apparatus for this heat exchange may be used and two modifications are illustrated in FIGS. 9 and l0, wherein like elements have been given like reference numerals.

In FIG. 9 the heat exchange is accomplished through the use of a countercurrent heat exchanger 46. Conduits 22 and 24 are led into heat exchanger 46 and are joined to and integral with any suitable heat exchange paths 27 and 29, respectively, in heat exchanger 46. Although these paths 27 and 29 are illustrated in the conventional way, it will be appreciated that one may be a coil (for example in a helical configuration) while the other may be defined as the path around the coil. In the arrangement shown in FIG. 9, an external load 48 is represented as comprising a suitable thermal conduit 49 bonded to the cold end of the heat exchanger and a conduit 50 for circulating a suitable heat transfer fluid.

In FIG. 10 there is shown an arrangement whereby the heat exchange is accomplished in what may be termed a combination countercurrent heat exchanger and regenerator designated as numeral 54. FIGS. l1 and 12 are horizontal and vertical cross-sections of this heat exchanger, respectively. Such a heat exchanger is typically in the form of two concentric shells 57 and 58 defining between them an annular space occupied by flat annular foraminous members 59 held in spaced relationship by suitable insulating spacers 60. The inner shell 58 also contains spaced foraminous discs 61 held apart by suitable spacers 62. In this type of heat exchanger one fluid would of course flow in one direction through the annular spacing while the other fluid would flow in the opposite direction in the central passage. As in the case of the heat exchanger in FIG. 9 the external load 55 is taken off at the bottom of heat exchanger 54 through a suitable thermal conduit 56.

The refrigeration cycle carried out in the apparatus in FIG. 9 is essentially the same as the basic cycle described above. The difference is that the heat exchange is accomplished in a countercurrent heat exchanger between the cold, low-pressure fluid leaving either subchambers 17 and 18 and the warm, high-pressure fluid entering either from subchamber 12 or 13. Refrigeration is extracted from the system through the heat exchanger 43 by means of a suitable heat exchange fluid circulated in line 50 which is in thermal contact with a thermal conduit 49 bonded to the bottom portion of the heat exchanger 46. 

1. REFRIGERATION METHOD, COMPRISING THE FOLLOWING STEPS: (A) DELIVERING HIGH-PRESSURE FLUID FROM A HIGH-PRESSURE FLUID SOURCE INTO COMMUNICATING FIRST AND SECOND SPACES AND COMPRESSING RESIDUAL LOW-PRESSURE FLUID IN SAID FIRST SPACE THEREBY TO HEAT SAID RESIDUAL FLUID, WHILE SIMULTANEOUSLY DISCHARGING HIGH-PRESSURE FLUID FROM COMMUNICATING THIRD AND FOURTH ENCLOSED SPACES INTO A LOW-PRESSURE REGION, THEREBY COOLING SAID FLUID IN SAID FOURTH SPACE; (B) CONTINUING DELIVERY OF SAID HIGH-PRESSURE FLUID FROM SAID HIGH-PRESSURE FLUID SOURCE AND TRANSFERRING HEATED FLUID FROM SAID FIRST SPACE TO SAID SECOND SPACE, WHILE SIMULTANEOUSLY CONTINUING DISCHARGING FLUID FROM SAID FOURTH SPACE THEREBY REDUCING ITS PRESSURE TO THAT OF SAID LOW-PRESSURE REGION AND SUPPLYING FLUID TO SAID THIRD SPACE WHERE IT BECOMES RESIDUAL FLUID; (C) THROUGHOUT DELIVERY AND DISCHARGE IN STEPS (A) AND (B) EXTRACTING HEAT FROM SAID HIGH-PRESSURE FLUID THEREBY TO COOL IT INITIALLY AND TRANSFERRING HEAT TO THE LOW-PRESSURE FLUID THEREBY TO HEAT IT INITIALLY; (D) EXPANDING SAID HIGH-PRESSURE FLUID IN SAID SECOND SPACE TO COOL IT FURTHER BY DISCHARGING IT INTO A LOWPRESSURE REGION, WHILE SIMULTANEOUSLY SUPPLYING HIGHPRESSURE FLUID FROM A HIGH-PRESSURE FLUID SOURCE TO SAID THIRD AND FOURTH SPACES AND COMPRESSING SAID RESIDUAL LOW-PRESSURE FLUID IN SAID THIRD SPACE DELIVERED THERETO IN STEP (B) THEREBY TO HEAT SAID RESIDUAL FLUID; (E) CONTINUING TRANSFER OF FLUID FROM SAID SECOND SPACE THEREBY REDUCING ITS PRESSURE TO THAT OF SAID LOWPRESSURE REGION AND SUPPLYING FLUID TO SAID FIRST SPACE TO BECOME SAID LOW-PRESSURE RESIDUAL FLUID OF STEP (A) WHILE SIMULTANEOUSLY CONTINUING DELIVERY OF SAID HIGH-PRESSURE FLUID FROM SAID HIGH-PRESSURE FLUID SOURCE AND TRANSFERRING HEATED FLUID FROM SAID THIRD SPACE TO SAID FOURTH SPACE; AND (F) THROUGHOUT DISCHARGE AND DELIVERY IN STEPS (D) AND (E) TRANSFERRING HEAT TO THE LOW-PRESSURE FLUID TO HEAT IT INITIALLY WHILE EXTRACTING HEAT FROM SAID HIGH-PRESSURE FLUID TO COOL IT INITIALLY, THEREBY ESTABLISHING THE CONDITIONS TO BEGIN STEP (A); SAID FIRST AND THIRD SPACES FORMING A SINGLE WARM ZONE, THE TOTAL VOLUME OF WHICH REMAINS CONSTANT, THE VOLUME OF EACH OF SAID FIRST AND THIRD SPACES VARYING DURING THE CYCLE; AND SAID SECOND AND FOURTH SPACES FORMING A SINGLE COLD ZONE, THE TOTAL VOLUME OF WHICH REMAINS CONSTANT, THE VOLUME OF EACH OF SAID SECOND AND FOURTH SPACES VARYING DURING THE CYCLE FROM ESSENTIALLY ZERO TO THE TOTAL VOLUME OF SAID COLD ZONE. 